case GLUT_SCREEN_WIDTH: return fgDisplay.ScreenWidth ;
case GLUT_SCREEN_HEIGHT: return fgDisplay.ScreenHeight ;
case GLUT_SCREEN_WIDTH_MM: return fgDisplay.ScreenWidthMM ;
case GLUT_SCREEN_WIDTH: return fgDisplay.ScreenWidth ;
case GLUT_SCREEN_HEIGHT: return fgDisplay.ScreenHeight ;
case GLUT_SCREEN_WIDTH_MM: return fgDisplay.ScreenWidthMM ;